30th April 2024

A 5-year-old child presents with high fever, cough, coryza, and conjunctivitis.

A 5-year-old child presents with high fever, cough, coryza, and conjunctivitis. Two days later, the child develops a blotchy red rash starting on the face and spreading downwards. Koplik spots are noted on the buccal mucosa. The child has not received measles vaccination.

Investigations:

Temperature: 39.5°C

Physical Examination: Cough, conjunctivitis, coryza, blotchy rash, and Koplik spots

Which investigation is most appropriate for confirming the diagnosis?